Driving simulation apparatus capable of scrolling at optimum speed

ABSTRACT

In a driving simulation apparatus for executing route retrieval on the basis of digital map data obtained by digitizing a road network, displaying the route so retrieved on a display unit and scrolling the map while tracing the route so displayed for simulation driving, the scrolling speed is changed in accordance with a reduced scale of the map displayed. When a wide area map is displayed, for example, an updating distance becomes long and when a detailed map is displayed, the updating distance becomes short. Therefore, even when the wide area map is displayed, the scrolling speed on the screen of the display unit does not become slow, and a long time is not necessary even when long distance retrieval is made.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Regarding so-called "navigation apparatuses", the present inventionrelates to a driving simulation apparatus for executing simulationdriving by tracing the result of route retrieval, and which is capableof rehearsing route guidance before drive is actually done.

2. Description of the Related Art

A so-called "navigation apparatus" is known which retrieves a route onthe basis of digital map data obtained by digitizing a road network anddisplays the route so retrieved on a display unit. A driving simulationdevice is also known which displays the result of route retrieval inthis navigation apparatus on a display unit and executes simulationdriving by tracing the route without actually driving a car.

In the driving simulation apparatus according to the prior art, aposition updating distance of driving simulation is fixed. Therefore,when long distance retrieval is made, an excessively long time isnecessary for the simulation from a start to a goal.

SUMMARY OF THE INVENTION

The present invention aims at providing a driving simulation apparatuscapable of executing simulation at an optimum speed.

In a driving simulation apparatus which executes route retrieval on thebasis of digital map data obtained by digitizing a road network,displays the route so retrieved on a display unit, conducts simulationdriving while tracing the route displayed on the display unit andscrolls the map, the object of the present invention described above canbe accomplished by changing the scrolling speed in accordance with areduced scale of a display map.

As an example of the change of the scrolling speed, an updating distanceis increased when the reduced scale of the display map is great and isdecreased when the latter is small. In other words, the updatingdistance becomes long when a wide area map is displayed and becomesshort when a detailed map is displayed. Therefore, even when the widearea map is displayed, the scrolling speed of the screen of the displayunit does not become low, and an excessively long time is not necessaryeven when a long distance retrieval is made.

When simulation is started, the cursor is moved to a position near thedesired start position on the route. When the operation is then started,simulation can be started from the desired start point.

In the present invention, further, when the cursor is set to a positionspaced apart from a predetermined value from the route at the start ofsimulation, simulation can be started from the start points of all theroutes. When simulation has been previously executed, simulation can bestarted, too, from the interruption point of previous simulation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object and features of the present invention will be moreapparent from the following description of the preferred embodiment withreference to the accompanying drawings, wherein:

FIG. 1 is a circuit diagram of a navigation apparatus;

FIG. 2A is a circuit diagram showing an example of a driving simulationapparatus according to the present invention;

FIG. 2B shows constitution of a start point judging unit in FIG. 2A.

FIG. 2C shows constitution of a driving coordinate generating unit 33 inFIG. 2A.

FIG. 3 is an explanatory view useful for explaining nodes and links;

FIG. 4 shows an example of a road map data structure;

FIG. 5 shows an example of a data format as a result of retrieval;

FIGS. 6 and 7 are flowcharts that together explain the processingoperation for setting a simulation start point in a driving simulationapparatus according to the present invention;

FIGS. 8A and 8B are explanatory views useful for explaining thecalculation method of the shortest distance in the processing shown inFIGS. 6 and 7;

FIG. 9 is a diagram showing the relation between the reduced scale of amap and a pitch in the processing shown in FIGS. 6 and 7;

FIGS. 10 and 11 are flowcharts that together explain the processing ofroute updating in the driving simulation apparatus according to thepresent invention;

FIG. 12 is an explanatory view useful for explaining a division methodof a route link in the processing shown in FIGS. 10 and 11;

FIG. 13 shows a screen of a display unit at a guide point; and

FIGS. 14A-14C shows a screen of a display unit when simulation isexecuted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be hereinafterexplained with reference to the accompanying drawings.

FIG. 1 is a structural view of a navigation apparatus.

In this drawing, reference numeral 1 denotes a central processing unitand reference numeral 2 denotes a communication bus. A present positiondetecting unit 3, a map recording unit 4 and a road information memoryunit 5 are connected to this communication bus 2. In the presentposition detecting unit 3, a GPS receiver 6 and a processing unit 7 areconnected to the communication bus 2. In the map recording unit 4, aprocessing unit 8 is connected to the communication bus 2.

A geomagnetic sensor 12 is connected to the processing unit 7 of thepresent position detecting unit 3 through an A/D converter 11, agyrosensor 14 is connected to the processing unit 7 through an A/Dconverter 13, a wheel speed sensor 16 is connected to the processingunit 7 through a pulse counter 15 and furthermore, a back gear signal 17is inputted to the processing unit 7. A GPS antenna 18 is connected tothe GPS receiver 6.

A road information reception unit 19 is connected to the roadinformation memory unit 5. A CD-ROM disk 22 is connected to theprocessing unit 8 of the map recording unit 4 through a decoder 21.

A main memory 23 that stores programs, data, etc., and an operation key24 for the input operation are connected to the central processingunit 1. A speech output unit 26 is also connected to the centralprocessing unit 1 through a speech output driving circuit 25, and adisplay unit 28 is connected through an image output unit 27.

FIG. 2A is a block diagram of the driving simulation apparatus.

Reference numeral 24 denotes an input unit, which is also used as theoperation key shown in FIG. 1. Reference numeral 4 denotes a maprecording unit and reference numeral 8 denotes a display unit. Theseunits 4 and 8 are the same as those shown in FIG. 1. Reference numerals31 to 34 denote the members which are included in the central processingunit 1 shown in FIG. 1, that is, a route retrieving unit 31, a startpoint judging unit 32, a simulation driving coordinate generating unit33 and a route guiding unit 34.

The start point judging unit 32 includes a shortest distance pointcalculating unit 321, a shortest distance calculating unit 322 and adriving simulation start point setting unit 323 as shown in FIG. 2B. Thesimulation driving coordinate generating unit 33 includes a scroll speedsetting unit 331, a guide display outputting unit 332 and a scrollstopping unit 333 as shown in FIG. 2C.

Next, the operation of the apparatus shown in FIG. 2A will be explained.

Setting of the start point and the goal point, setting of manual scroll,if any, and inputting of the start/end of driving simulation are carriedout by using the inputting unit 24.

The route retrieving unit 31 executes the shortest route retrieval suchas obtaining the distance, time, etc., on the basis of the informationbetween the start and the goal that is inputted from the inputting unit24 and on the basis of the network information stored in the maprecording unit 4.

As shown in FIG. 3, the map data stored in the map recording unit 4 andused for the route retrieval described above comprises a node having theposition information and the connection information of the roads, and alink having the distance information between the nodes and attributeinformation.

The format of the map data is shown in FIG. 4. The map data 37 includesa header, a node table, a link table and an adjacent node table as shownin FIG. 4. The content of the header and the content of each table areshown on the right-hand portion of the drawing.

FIG. 5 shows the data format obtained as a result of retrieval. Theretrieval result data format 38 includes a header, a unit data table asthe route information from the start to the goal, a coordinate table, aguide point data table as the guide information, and a road data table.The content of the header and that of each table are shown on theright-hand portion of the drawing.

When route retrieval is completed, the route as the result of retrievalis displayed on the screen of the display unit 28 with the scroll cursorSC. Next, the start point judging unit 32 judges the start position ofdriving simulation. FIGS. 6 and 7 show the flowchart for this judgement.

Steps S11 to S16 determine the shortest distance between the scrollcursor SC and the links of all the routes, and decide the link numberproviding the shortest distance and its position.

At the step S11, the maximum numerical value 0xffff is set to a registerminLen for storing the shortest distance, 0 is set to a register minNumfor storing the number of the link of the shortest distance point, and 0is set to a register i for storing the link number which is now beingjudged.

At the next step S12, the shortest distance len between the coordinatesof the link having the number stored in the register i and thecoordinates of the cursor SC. This calculation method is shown in FIGS.8A and 8B. FIG. 8A, (a) represents the calculation method of theshortest distance point in the ordinary case, and FIG. 8B represents thecalculation method of the case where the end point of the link is theshortest distance point. In the drawing, symbol SC represents the scrollcursor and its coordinates are (carX, carY). Symbol S represents thestart point of the link and its coordinates are (sx, sy). Symbol Erepresents the end point of the link and its coordinates are (ex, ey).Symbol H represents the shortest distance point and its coordinates are(xx, yy). Symbol len represents the distance between the cursor SC andthe shortest distance point H and len 2 represents the distance betweenthe start point of the link S and the shortest distance point H. Thecalculation formulas for calculating the shortest point in each caseare, respectfully, shown in FIGS. 8A and 8B. Further, the shortestdistance len can be calculated in accordance with the following formula:##EQU1##

At the step S13, whether or not the shortest distance len from thecursor SC is smaller than the value stored in the register minLen isjudged. Here, if the shortest distance len calculated this time issmaller than the shortest distance previously obtained, the flowadvances to the step S14, and the content of each register is updated.If it is greater, the flow advances to the step S15 while skipping thestep S14.

At the step S14, the shortest distance len obtained this time is storedin the register minLen, and the coordinates (xx) and (yy) of theshortest distance H are stored in the registers minX and minY. Thenumber i of the link at this time is also stored in the register minNum.

At the step S15, +1 is added to the content of the register i, and theflow then advances to the step S16. Consequently, judgement of the nextlink is effected at the steps after the step S12 in the next processing.

At the step S16, whether or not the link of this time is the last linkis judged, and if it is not, the flow returns back to the step S11. Whencalculation of all the links is completed, the flow advances to the stepS17.

As a result of the processings up to the step S16 described above, theshortest distance len is set to the register minLen, the number of thelink of the shortest distance point is set to the register minNum, andthe coordinates of the start point of the link are set to the registersminX and minY, respectively.

At the step S17, whether or not the value of the register minLen issmaller than a predetermined value AREA-MAX is judged. If the result isYes, the flow advances to the steps S19 et seq, and the processing forsetting the shortest point to the start point of driving simulation isexecuted. If the result is No, the flow advances to the steps S18 etseq, and the processing for setting the shortest point to the point atwhich simulation is previously interrupted or to the start point of allthe routes is executed.

At the step S19, the pitch of position updating in driving simulation isset in accordance with the reduced scale of the map.

This setting of the pitch will be hereby explained. A map having ahierachical structure including a map of a broad area such as anation-wide map and a detailed map such as a town map of Kobe City, forexample, is used as the map for the navigation apparatus, and this maphas different reduced scales. If the updating distance of simulation isfixed as in the prior art apparatuses, the scrolling speed of the screenbecomes different with each map when the maps having different reducedscales are displayed on the display unit 28. Particularly when longdistance retrieval is conducted, an excessively long time is necessaryfrom the start to the goal.

In contrast, when the maps 41 to 44 having the hierachical structurehaving different reduced scales exit as shown in FIG. 9, the pitch isreduced so as to shorten the updating distance when the detailed map 41is displayed, and is elongated so as to elongate the updating distancewhen the broad area map 44 is displayed, in accordance with the reducedscale of each map. In this way, the scrolling speed on the screen whensimulation is made becomes constant even when the reduced scales of themaps are different, and simulation can be executed at an optimum tracingspeed from the detailed map 41 to the broad area map 44.

At the subsequent step S20, the distance len 2 between the coordinates(sx, sy) of the start point of the link having the number stored in theregister minNum and the shortest distance point H represented by theregisters minX and minY.

At the step S21, the number of the register minNum is set to theregister startNum representing the start point of simulation, thedivision number j (=len 2/PITCH) is calculated, and the processing iscompleted. The division number j of the link will be described later.

At the step S18, whether or not simulation is previously made is judged.If the result proves Yes, the processing is as such completed. Ifsimulation is previously made, the value stored in the register startNumrepresents the number of the interruption point in previous simulation.Therefore, the simulation start point is set to the interruption pointwithout making any setting at all at the steps after the step S18.

If the result is No at the step S18, the register startNum for storingthe start point is reset by 0, and 0 is set to the division number j ofthe link. In this way, the cursor is set independently of the route, andif simulation is not previously made, the start point becomes the startpoint of all the routes.

When the start point of simulation is set by the processings shown inFIGS. 6 and 7, the start command is inputted from the inputting unit 24.Then, simulation is started, and position updating is conducted by theflowchart shown in FIGS. 10 and 11, and scroll of the screen of thedisplay unit 28 is made.

The processing shown in FIGS. 10 and 11 is started at a predeterminedtime interval.

At the step S30, whether or not the driving simulation stop signal isinputted from the inputting unit 24 is judged. If this signal is notinputted, the flow advances to the step S31. If this signal is inputted,this processing is stopped.

At the step S31, setting of PITCH is conducted in accordance with thereduced scale of the map. The reason why this pitch is set has alreadybeen explained with reference to the step S19 shown in FIG. 7.

At the step S32, 0 is set to the register leng as initial setting, andthe value of startNum obtained by the processing shown in FIGS. 6 and 7is set to the register i.

At the step S33, the coordinates of the start point of the link havingthe number stored in the register i are set to (x_(i), y_(i)), and thecoordinates of the start point of the subsequent i+1th link are set to(x_(i+1), Y_(i+1)), and these coordinates are then read.

At the step S34, the line segment 1_(i) between the coordinates (x_(i),y_(i)) and the coordinates (x_(i+1), y_(i+1)) and its direction dir_(i)are calculated.

At the step S35, whether or not the ith route is the guide point (forexample, crossing) is judged with reference to the data shown in FIG. 5.If the result is Yes, the flow advances to the step S36 and if it is No,the flow advances to the step S43.

At the step S36, the line segment 1_(i) obtained at the step S34 isadded to the content of the register leng. At the next step S37, whetheror not the value of the register leng is greater than twice of the pitchPITCH is judged. If the result is No, 1 is added to the register i atthe step S44 and then the flow returns to the step S33. If the result isYes, the flow advances to the step S38.

At the step S38, whether or not the line segment 1_(i) obtained at thestep S33 is greater than twice the pitch PITCH is judged. If the resultis No, the flow advances to the step S43, and if it is Yes, the flowadvances to the step S39.

At the step S39, the line segment 1_(i) is divided by the pitch PITCH.The result of this division is shown in FIG. 12. The line segment 1_(i)connects the coordinates (x_(i), y_(i)) of the start point of the ithline to the coordinates (x_(i+1), y_(i+1)) of the start point of thesubsequent link, and among the points divided by the pitch PITCH, theith coordinates are expressed by (x_(ij), y_(ij)).

At the step S40, (x_(ij)), (y_(ij)) and dir_(i) are set to the registeroutX, the register outY and the register outDir, respectively, on thebasis of the ith coordinates (x_(ij), y_(ij)) among the coordinates ofeach point obtained by equally dividing the line segment 1_(i) by N.

The simulation driving coordinate generating unit 33 updates the routeposition on the basis of these outX, outY and outDir.

Whether or not the value of the register j reaches the division number Nis judged at the step S41. If the result is No, the flow advances to thestep S45. If the result is Yes, the flow advances to the step S42, where1 is added to the content of the register i, the register j is reset to0, and then the flow advances to the step S45. The value of the registeri is set to the register startNum at this step S45.

When the distance of the link is greater than PITCH×2 by the processingdescribed above, the link is divided into N as shown in FIG. 12, theroute position updating is effected for each pitch, and the screen ofthe display unit 28 is serially scrolled. Therefore, the scrolling speedcan be made constant irrespective of the length of the link.

When this ith route is judged as not being the guide point at the stepS35, and when the distance of the link is judged as not being greaterthan twice the pitch PITCH at the step S38, the values(x_(i))+(x_(i+1))!/2, (y_(i))+(y_(i+1))!/2 and dir_(i) are set to theregister outX, the register outY and the register outDir, respectively,at the step S43, 0 is set to the register j, and 1 is added to thecontent of the register i. At the step S45, the value of the register iis set to the register startNum.

The processing described above, which passes through the step S43,updates the route position so that the cursor SC is positioned at anintermediate point of the next point when the passing node does notinclude the guide point and when the length of the link is small evenwhen the passing node includes the guide point, and the screen of thedisplay unit 28 is scrolled.

At the step S46, whether or not the ith route is the guide point isjudged. If the result is No, the processing is completed, and if theresult is Yes, the route guide display is displayed on the display unit33 at the step S47, and the passage of a predetermined time is awaitedat the step S48. In this way, the route guide display is continuouslydisplayed for a predetermined time, and the user can more easily watchthe screen.

The processing in FIGS. 10 and 11 explained above is started in everypredetermined time interval, and the screen of the display unit 28 isscrolled at a predetermined pitch.

Since scrolling is stopped while the stop signal is inputted from theinputting unit 24 at the afore-mentioned step S30, the same screen canbe continuously displayed at an arbitrary timing on the display unit 28.

Next, when the cursor SC comes near to the guide point, the routeguiding unit 34 executes the net guide.

First, the speech output unit 26 outputs a chime sound "PUOOON" and thenoutputs the speech "Turn to the right about 300 m ahead". Next, a guidesign 51 is displayed as shown in FIG. 13, a crossing enlarged view 52with a landmark is displayed and then a distance display 53 to the guidepoint is displayed.

FIGS. 14A-14C shows the screen of the display unit 28 when drivingsimulation is executed. FIG. 14A shows the state where the cursor SC,before the start of simulation, is put on the route 61. By the way,reference numeral 62 denotes the relay point. When the start button ofthe input unit 24 is pushed under this state, the cursor SC changes to acar mark 63 as shown in FIG. 14B, and an arrow 64 representing thedriving direction is displayed. The screen is then scrolled, the relaypoint gradually approaches the car mark 62, and a display reading "300 mto the relay point" is displayed at the lower portion 65 of the screen.

The screen is further scrolled and when the mark 63 comes near to therelay point, a display reading "0 m to the relay point" is displayed atthe lower portion 65 of the screen.

According to the present invention, it is possible to obtain a drivingsimulation apparatus capable of executing simulation at optimumscrolling speed.

I claim:
 1. A driving simulation apparatus comprising:means forretrieving a route based on digital map data obtained by digitizing aroad network; means for displaying the route so retrieved on a displayunit; means for scrolling the map while tracing the route displayed onsaid display unit for simulation driving; and means for automaticallysetting an updating distance in accordance with a reduced scale of a mapto be displayed.
 2. A driving simulation apparatus according to claim 1,wherein said means for automatically setting an updating distanceincreases an updating distance when the reduced scale of a display mapis great and decreases the updating distance when the reduced scale issmall.
 3. A driving simulation apparatus according to claim 1, whichfurther comprises means for displaying a route guide for an arbitrarytime during simulation.
 4. A driving simulation apparatus according toclaim 1, which further comprises means for stopping scrolling of the mapduring simulation in accordance with an input signal.
 5. A drivingsimulation apparatus according to claim 1, which further comprises a maphaving a hierachical structure having different reduced scales as saidmap.
 6. A driving simulation method comprising:executing route retrievalbased on map data obtained by digitizing a road network; displaying theroute so retrieved on a display unit; scrolling the map while tracingthe route displayed on said display unit for simulation driving; andautomatically setting an updating distance in accordance with a reducedscale of a map to be displayed.